Trayvon Martin was killed on his way back from the shops by neighbourhood watchman George Zimmerman. Photograph: Reuters

The image of a young black man that came up on the muted TV immediately caught my attention. It was a strange combination of my two children, and I knew the news was not good. I turned the sound up, and got the facts about 17-year-old Trayvon Martin, killed on his way back from the shops by self-appointed neighbourhood watchman George Zimmerman, who claimed he had felt "threatened" by the teenager, who "looked suspicious".

But what was so suspicious about him? It seems to me that it was nothing more than the prejudice that a young black man walking around an exclusive Florida neighbourhood had to be "up to something", to use Zimmerman's words. There was no way that he was supposed to be there – even though it was where his father lived.

And it's not just me: 1.5 million people have signed a petition calling on Zimmerman to be prosecuted for a racially motivated murder. Police have not arrested Zimmerman, who has found shelter in "stand your ground" laws, which supposedly protect those who kill in self-defence. Zimmerman effectively employed the same racial profiling that means black people in the UK are 30 times more likely to be stopped and searched than white people because police feel some vague suspicion.

Like every black parent in Britain, I've had to have "the talk" with my kids when they reach a certain age. Not the one about the birds and the bees, but the one where you prepare them for stop and search. You advise them what to do if it happens and you give them tips on what to do to avoid it. Don't run in the street because you may look suspicious. People may think that you are fleeing the scene of a crime. Don't hang around in the streets. Our young men are labelled as troublemakers, lazy and no good.

Who can forget the infamous words of David Starkey, when he declared of last summer's rioters "the whites have become black"? In other words, black kids, you're damned if you do and damned if you don't. Even when white children misbehave it is your fault. I wonder if Starkey saw the images from Spain yesterday and concluded that the Spanish have become black, too.

It is precisely this attitude that I can no longer tolerate. I don't want parents having to panic when their son goes out to school, work or to run an errand. I want our kids to have a fair chance and not be criminalised because of the colour of their skin. Kids who run around playgrounds today will soon be told to suppress this natural instinct less they should look suspicious.

We want the state of Florida to know that the world is watching and we want them to do the right thing by this young man. We protest for every black man and boy who has been killed wrongfully in this country, both in and out of police custody, in prison, in psychiatric care and those stopped and searched because they look "suspicious". To remember the "not enough evidence" to prosecute, the "open verdict" cases, the "accidental deaths" or the "death by misadventure", the "unsolved", the "verdict unknown", and for all of the families who must suffer the injustice.

Martin Luther King Jr said: "Injustice anywhere is a threat to justice everywhere". We are all Trayvon Martin.